Problem: N different natural numbers are given. If you select four different ones and set them as $ A $, $ B $, $ C $, $ D $, the following formula

$ \ Frac {A + B} {C --D} $



I want to find the maximum value of.




Given N different natural numbers, choose 4 different from them and create a program to find the maximum value of the above formula.



Input

The input is given in the following format.


N
a1 a2 ... aN


The number N (4 ≤ N ≤ 1000) of natural numbers is given in the first line. The value ai (1 ≤ ai ≤ 108) of each natural number is given in the second line. However, the same natural number does not appear more than once (ai ≠ aj for i ≠ j).

Output

Outputs the maximum value of the above formula as a real number for a given N natural numbers. However, the error must not exceed plus or minus 10-5.

Examples

Input

10
1 2 3 4 5 6 7 8 9 10


Output

19.00000


Input

5
22 100 42 3 86


Output

9.78947


Input

6
15 21 36 10 34 5


Output

18.00000


Input

4
100000 99999 8 1


Output

28571.285714

Solution (in CPP):

Solution:
#include <iostream>
#include <algorithm>
#include <iomanip>
using namespace std;

int main() {
	int n;
	int a[1000];
	double r = 0;

	cin >> n;

	for(int i = 0; i < n; i++)
		cin >> a[i];

	sort(a, a + n);

	for(int i = 0; i < n - 1; i++){
		double rt;
		if(i < n - 3)
			rt = (double) (a[n - 2] + a[n - 1]) / (double) (a[i + 1] - a[i]);
		else if(i == n - 3)
			rt = (double) (a[n - 4] + a[n - 1]) / (double) (a[i + 1] - a[i]);
		else if(i == n - 2)
			rt = (double) (a[n - 4] + a[n - 3]) / (double) (a[i + 1] - a[i]);

		if(rt > r)
			r = rt;
	}

	cout << setiosflags(ios::fixed | ios::showpoint) << setprecision(6) << r << endl;

	return 0;
}